The report by ISO New England says natural gas-fired power plants generated just over half of the electricity produced in the region last year. So a nearly 20 percent decline in the average price of natural gas in 2012 helped pull down electricity prices 23 percent, in what the ISO said was the acceleration of a recent trend.

The report noted that the flip side of lower prices — increased demand for natural gas — continues to strain regional pipeline capacity. It said at times last year, natural-gas fired generators couldn't operate because the fuel wasn't available.

The report also said overall electricity consumption dropped by nearly 1 percent last year.